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attester: az_snp_vtpm: Check cpuid bits in detect_platform() #169

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attester: az_snp_vtpm: Check cpuid bits in detect_platform() #169

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3 changes: 2 additions & 1 deletion attestation-agent/attester/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@ az-snp-vtpm = { git = "https://github.com/kinvolk/azure-cvm-tooling", rev = "2c2
base64.workspace = true
log.workspace = true
occlum_dcap = { git = "https://github.com/occlum/occlum", rev = "dbe404f", optional = true }
raw-cpuid = { version = "11", optional = true }
serde.workspace = true
serde_json.workspace = true
sev = { git = "https://github.com/virtee/sev", rev = "3dca05d2c93388cb00534ad18f5928fd812e99cc", optional = true }
Expand All @@ -23,5 +24,5 @@ all-attesters = ["tdx-attester", "occlum-attester", "az-snp-vtpm-attester", "snp

tdx-attester = ["tdx-attest-rs"]
occlum-attester = ["occlum_dcap"]
az-snp-vtpm-attester = ["az-snp-vtpm"]
az-snp-vtpm-attester = ["az-snp-vtpm", "dep:raw-cpuid"]
snp-attester = ["sev"]
34 changes: 32 additions & 2 deletions attestation-agent/attester/src/az_snp_vtpm/mod.rs
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Expand Up @@ -7,11 +7,41 @@ use super::Attester;
use anyhow::*;
use az_snp_vtpm::{imds, vtpm};
use log::debug;
use raw_cpuid::{cpuid, CpuId, Hypervisor};
use serde::{Deserialize, Serialize};
use std::path::Path;

pub fn detect_platform() -> bool {
if let Err(err) = vtpm::get_report() {
debug!("Failed to retrieve Azure HCL data from vTPM: {err}");
if !Path::new("/dev/tpm0").exists() {
debug!("vTPM device not found");
return false;
}

let cpuid = CpuId::new();
let Some(hyper_info) = cpuid.get_hypervisor_info() else {
debug!("Not a VM");
return false;
};
let hypervisor = hyper_info.identify();
debug!("Hypervisor: {:?}", hypervisor);
if hypervisor != Hypervisor::HyperV {
return false;
}

const HYPERV_CPUID_FEATURES: u32 = 0x40000003;
const HV_ISOLATION: u32 = 1 << 22;
let hv_features = cpuid!(HYPERV_CPUID_FEATURES);
if hv_features.ebx & HV_ISOLATION == 0 {
debug!("VM is not an isolation VM");
return false;
}

const HYPERV_CPUID_ISOLATION_CONFIG: u32 = 0x4000000C;
const HV_ISOLATION_TYPE: u32 = 0xF;
const HV_ISOLATION_TYPE_SNP: u32 = 2;
let hv_isol_config = cpuid!(HYPERV_CPUID_ISOLATION_CONFIG);
if hv_isol_config.ebx & HV_ISOLATION_TYPE != HV_ISOLATION_TYPE_SNP {
debug!("VM is not an SNP VM");
return false;
}
true
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